Sugar decolorization



' Patented Nov. 4, 1947 SUGAR DECOLORIZATION arcliil' Manor. N. Y., assignor' to The Mathleson Alkali Works, Inc.,

George P. Vincent, Bri

l\lew York, N. Y., a

corporation of Virginia No Drawing. Application May 17, 1944, Serial No. 536,029

s'cisi s. (Cl. 127-48) This invention relates to the refining of sugar.

compositions and more particularly to improved methods of treating sugar compositions for the purpose of removing or modifying the character of impurities contained therein and of preserving such sugar compositions.

Unless properly refined, sugar and sugar syrup will contain objectionable impurities, including color bodies, either naturally present in the sugar juices or developed during the" refining operation. They are also subject to the deteriorating action of yeast, mold and bacteria.

The operation of removing such objectionable impurities is generally referred to in the industry as bleaching. However, the term bleaching as used in the sugar industry usually indicates clarification and purification generally and is not restricted to an improvement in color.

For many years, the decolorization of sugar compositions dependent upon defecation followed by treatment with bonechar. Then, over a period of years, the use of activated decolorizlng carbon supplanted the use of bonechar to an important extent. Several years ago, it was proposed to treatthe sugar composition chemically prior to treatment with the carbon. Economic margins in sugar refining are narrow, small differentials in cost thus becoming important, and consequently these advances in the art of refining sugar have found a place in practical operations only to the extent that they developed economic advantages. By supplementing the defecation and carbon treatment of sugar compositions, for instance sugar melts and sugar syrup, by a treatment with a chemical refining agent, the character of the impurities is modified so that their subsequentremoval from the sugar composition by precipitation and adsorption is facilitated.

One of the chemical refining agents previously proposed for the treatment of sugar compositions is calcium hypochlorite, and satisfactory operations by which the sugar compositions have been bleached, clarified, and purified by treatment with.

calcium hypochlorite, followed by defecation and carbon treatment, have been developed. The use of "calcium hypochlorite has also been proposed in the sterilizing and preserving of sugar composition to kill or prevent the growth of bacterial bodies, and the like.

The present invention is based on my discovery that improved results in the refining and preservation of sugar composition may be obtained by the substitution of a chlorite, sodium chlorite or calcium chlorite forinstance, for all or a substantial proportion of the hypochlorite previously proposed.

The use of a chlorite in the refining of sugar, either alone or together with a hypochlorite, affords several important advantages. For example, in operations comprising the treatment of a sugar melt with the chemical reagent followed by treatment with activated decolorizing carbon, I have found that substantially the same decol orizati'on can be effected by substituting a relatively small proportion of a chlorite for a relatively large proportion of the calcium hypochlorite previously used, with a substantially reduced consumption of total chemical reagent, i'. e., hypochlorite plus chlorite, measured either in terms of total weight of reagents or total available chlorine. In operations of this sort, the chlorite has been found to be more effeclive when used in conjunction with a hypochlorite than when used g the impurities present in alone.

I cannot state positively the mechanism of the reaction involved, but apparently the chlorite is in some way activated by the presence of the hypochlorite. Instead of treating the sugar composition with a chlorite in conjunction with a hypochlorite, other means of activating the chlorite may be employed. In neutral Or alkaline solutions, the chlorites alone are relatively inactive or react very slowly. However, various means are known whereby the chlorites maybe activated, for instance, by the presence of a hypochlorite or of elemental chlorine or by maintaining the pH of the treating solution on the acid side by the addition of an acid or an acid salt. Usually, in the treatment of sugar compositions, a strongly acid condition is undesirable, as it tends to promote inversion of the sucrose. However, mildly acid conditions are frequently unobjectionable and, where permissible, the action of the chlorite may be expedited by such condition without resort to use of a hypochlorite or any other activating agent; Under such mildly acid conditions, the chlorites may be. used eilectively in the bleaching and refining of sugar or as a sterilizing agent and preservative of sugar compositions.

By treating a sugar melt with a hypochlorite in the refining or so-called bleaching operation, the sugar melt are so modified as to render them less objectionable and generally more susceptible to separation by precipitation and adsorption by the defecation and carbon treatment. By such treatment with a hypochlorite, a substantial improvement in the color of the sugar melt is usually obtained. However, the modified impurlties resulting from the treatment of the sugar melt with a hypochlorlte has been found to be relatively unstable and, if

the sugar'melt is subsequently heated to an elevated temperature during the subjection of the melt to defecation or filtration. the impurities present have been found to revert to a substantial extent to objectionable color bodies. Further, even after defecation and filtration, the resultant sugar composition has been found to darken materially when subiected to elevated temperatures, such as employed in the conventional Candy test, which involves boiling under atmospheric pressure to a temperature of 118. C.

In accordance with my present invention, whereby the sugar composition is treated with a chlorite, the modified impurities appear to be of a much more stable character much less readily reconverted to objectionable color bodies. Further, the finished sugar product refined in accordance with my present invention, after defecation and carbon treatment, has been found to have improved color and to be much more stable with respect to color, as when subjected to the candy test. Because of the more stable character of the sugar composition resulting from treatment with a chlorite, higher temperatures may be employed in the defecation and filtration of the sugar melt and the refining of the sugar is thereby facilitated.

In the so-called bleaching of sugar melts in I accordance with my present invention, the sugar phate defecating agent and thereafter treated with an adsorbent, for example activated decolorizing carbon. The hypochlorite-chlorite treatment is with advantage carried out at a temperature approximating TO-110 F. The precise order in which the several treated agents are added to the melt in the chemical treatment is not essential but certain advantages are secured by adding the calcium hypochlorite after the phosphate defecating agent, particularly if the chlorite used is sodium chlorite. The products of defecation are with advantage separated from the melt prior to treatment with the adsorbent.

The chemical treatment of my invention may with advantage be applied directly to light-colored sugar melt. With dark melts it is usually advantageous to subject'the melt to treatment with lime and a phosphate defecating agent and to separate the products of this defecation prior to the chlorite treatment.

In referring to chlorites herein, I refer particularly to the chlorites of the alkali and alkaline earth metals, for instance sodium chlorite, NaClOs, and calcium chlorite, Ca(CiOa)z. In referring to phosphate defecating agents, I refer to the known defecating agents of this class such as sodium phosphates, acid calcium phosphates and phosphoric acid. In referring to adsorbents, I refer to adsorbents such as activated decolorizing carbon, bonechar and calcined bauxite.

It will be understood that my invention is applicable to a wide variety of sugar refining operations. It will, however, be further described in more detail in connection with particular embodiments which illustrate the application of my invention to sugar melts produced from raw sugar.

Starting with raw cane sugar, the sugar is washed, for example, in centrifugals, as in conventional practice. The washing operation produces a washed raw sugar and afllnations, the latter being handled in the conventional way. The washed raw sugar is then melted with water to form the melt to be treated and decolorized. This melting operation may be carried out at moderate temperature or it may be carried out at elevated temperature and the melt subsequently cooled to the temperature appropriate for further processing. The washed raw sugar may be melted in water or in sweet water, water containing some sugar value from some other step in the sugar refining operation. Where a hypochlorite is to be used in conjunction with the chlorite, the pH value of the sugar melt is with advantage then adjusted, for example by the addition of lime water, so that at no time during the further processing will the pH value of the melt drop below about 6.8 or some higher minimum limit. The pH value of the melt may thus, for example, be brought to a point approximating 7.5 to 9.5. This adjustment of the pH value of the melt is made to avoid sugar loss by inversion. At this point, the sugar melt may for example be of a density corresponding to 60 Brix, although my invention is not limited in application to melt or syrup of any particular concentration.

If the melt is relatively light in color, calcium acid phosphate, sodium chlorite and calcium hypochlorite are added in the order named and the resulting reactions are allowed to proceed, for example for 1 hour at a temperature of 85 F. to 95 F. The sodium chlorite may be the commercial product containing for example 130% available chlorine and the calcium hypochlorite may be for example a commercial product containing 70% available chlorine. The proportions of the several ingredients, in percentages by weight on the sugar solid present, may approximate for example; for sodium chlorite 0.0088%, for calcium acid phosphate 0.027% and for calcium hypochlorite 0.065%. However, these proportions are subject to considerable variation.

If the sodium chlorite is used and if the calcium hypochlorite is added after the acid calcium phosphate, as indicated, bubbles of gas liberated in the reactions will attach themselves to the particles of solid precipitate forming through the melt with the result that the products of defecation will, with reasonable care, be carried to the surface of the melt in the treating receptacle as a foaming scum from which the clear treated liquid can be readily separated by decantation. If the calcium hypochlorite is added before the acid calcium phosphate, or if precipitation is initiated as by the use of calcium chlorite prior to the introduction of calcium hypochlorite, this result is not uniformly attained and some other or some supplemental means of separating the products of defecation must be used. The products of defecation, for example, can be separated by filtration and in such filtration it is advantageous to use a filter aid such as diatomaceous earth.

The sugar melt is then treated with an adsorbent, with particular advantage with activated decolorizing carbon, as in conventional practice. For example, the sugar melt following separation of the products of defecation may be treated with 0.1% of activated decolorizing carbon for a period ,of 10 to 15 minutes, at a temperature of to F. The carbon treatment may also be carried out for longer periods and at higher temperatures, periods of treatment as long as onehour or more and temperatures as high as 200 to 210 F. are useful. Following this treatment, the suspended carbon is separated as in conventional practice, for example, by filtration. The filtrate l5- constitutes the refined and decolorized product.

It the melt, following adjustment of the pH value, is rather dark in color, it is usually advantageous to subject it to a preliminary defecation before subjecting it to the chlorite-hypochlorite treatment. For example, this preliminary defecation may be carried out by addition of lime and calcium acid phosphate or phosphoric acid,

my present invention, by subjectin the sugar composition to the action of the chlorite under mildly acid conditions or by treating the sugar composition with a chlorite in the presence of a hypochlorite, or other activating agent, in alkaline solution. As previously noted, where the as defecation is conventionally practiced, in conjunction with the use of bonechar or activated carbon. Also. if the melt is rather dark in color, the proportions of the several treating reagents may be increased. For example, the proportions may approximate; for sodium chlorite 0.026%,

for calcium acid phosphate, 0.073%; and, for calthe proused may taken to maintain the pH value above the selected minimum. If the bonechar has too great an eflect in reducing the pH value of the'melt, calcium carbonate or bauxite may be added to the bonechar, assupplied to the treatment or prior chlorite is used alone, theaction is relatively slow and time-consuming but advantages are attained, even under such conditions, where a sufflcient time factor is permissible.

The improvement-in color by treatment with the chlorite, until followed by the carbon treatment, is usually less than that obtained by treatment with hypochlorite alone. However, the color of the sugar composition treated with chlorite in accordance with my present invention, even in the absence oi the carbon treatment, is more to revivification, or the bonechar may be somewhat overburned during reviviflcation.

Proceeding as described, I have been able to effect the same decolorizations with about onehalf the consumption of chemical reagentsand with from about one-third to less than one-fifth of the consumption of the adsorbent, activated decolorizing carbon for example, required to attain the result by conventional practice. The economic advantage of such savings with respect to carbon or other absorbents required will be self-apparent. Even though the cost per unit of available chlorine as chlorite is greater than that as hypochlorite, I have by my invention been able to reduce the cost of chemical reagents, as distinguished from carbon and other adsorbbents, to one-half or less.

The refined and decolorized melt can be used as a syrup, as-is. or following further concentration or dilution, or the refined decolorized melt may be subjected to concentration and crystallization, for example by multiple-effect evaporators followed by a vacuum pan crystallizer and granulating and cooling, as in conventional practice, to produce the sugar of commerce. My invention is applicable to syrupsor other melts whether or not they are produced from raw sugar and to sugar compositions generally irrespective of their particular concentration, provided only that they are melts, that is liquid, under the conditions required for the processing. The economies of my invention are more fully developed in application to melts of relatively high density, 45 to 55 Brix or higher, for example.

The invention is particularly applicable to refining operations, such as described, comprising the treatment of the composition with a phosphate defecating agent or the like and subsequent treatment with decolorizing carbon. However, even in the absence of the defecation and carbon treatment, a noticeable improvement in color of sugar compositions is effected, in accordance with stable and less readily affected detrimentally. by elevated temperatures than that resulting from treatment with a hypochlorite. Further, the modified impurities resulting from with a chlorite are more susceptible'to separation by defecation and adsorption than are the -modified impurities resulting from the hypochlorite treatment. Due to the greater susceptibility of the sugar melt to further improvement in color by treatment with decolorizing carbon and to greater temperature stability, a sugar melt treated in accordance with my present invention and subsequently treated with carbon and subiected to the conventional Candy test, has been found to have a substantially better color than a sample or the same melt treated with hypochlorite alone and subsequently treated with carbon, even prior to the Candy test.

For instance, two samples of a, sugar melt were identically treated except that one was subjected to a chemical treatment with calcium hypochlorite alone and the other to a chemical treatment with chlorite and hypochlorite. The colors (by the Home scale) of the respective samples: after the indicated stages of the treatment, are set forth in the following table:

Calcium Calcium Hvpochlorite+ Chemical Agent Hypochlorite I Chlorite Alone Alter chemical treat- Very light Darker than when treated me with hypochlorite alone. After filtering through 0.02 0.38. I

carbon. Alter Candy 'lest 1.67 0.58.

This and similartests have'shown that the chemical effect of the chlorite on the impurities in the sugar is substantially 'difierent from the effect of the hypochlorite, that the impurities in sugar compositions treated with a chlorite are much more susceptible to removal by theconventional carbon treatment than those of sugar compositions treated with hypochlorite alone and that, as shown by the foregoing tabulation, the color of the sugar composition treated in accordance with my present invention is, after the Candy test, superior to that of a corresponding sugar composition treated in the conventional way, using calcium hypochlorite even before subjectiontothe Candy test.

The effectiveness of the chlorite, used accordance with my present invention in conjunction with hypochlorite, is so much greater than that of the hypochlorite alone that 50% or more of the hypochlorite formerly used may be replaced by about onesixth the weight of the chlorite. Further, as previously noted, the amount of the treatment 7 decolorizing carbon required may also be materially reduced.

Though the invention has been specifically i1- lustrated by operations in which the chlorite was used in conjunction with hypochlorite, it will be understood that the concurrent use of hypochlorite is not essential but that, as previously noted,

other means of activating the chlorite may be employed.

' For example, to a 200-gram portion 01' a. 55 Brix sugar melt, containing 110 grams oi washed sugar and having a pH of 6.3 and a temperature of 32 0., there wasadded 1 c. c. of a 10% solution of sodium chlorite, 0.6c. c. of a 10% solution of Ca(H)z and 0.12 gram of Cil(H2PO4) 2. This mixture was heated to 70 C. and a precipitate formed which rose to the top of the liquid. The sugar melt thus clarified was found to be a very light color, much lighter than originally. Thereafter, the solution was treated with 0.5% activated decolorizing carbon at 85 to 90 0., for about 10 minutes and filtered, the pH of the melt being 6.2. By this carbon treatment, a further substantial improvement in color was obtained.

In a further operation, 1 c. c. of 10% sodium chlorite solution was added to a sugar melt at room temperature having a pH of 4.8-5 and prepared by diluting 150 grams oi. a 73 Brix melt to 55 Brix. After standing overnight, the mix was found to be considerably lighter than a blank similarly treated and showed no sign of fermentation while the blank sample under similar conditions showed definite fermentation.

As an illustration of the effectiveness of chlorite as a preservative of sugar compositions, a heavy invert melt was prepared by blending a straight sucrose solution with an invert melt. The density of the blend was reduced to about 71 Brix and the pH adjusted to about 5 by the addition of NaaPO4. To separate samples of the 1 resultant sugar composition, there was added the following:

Samples A. 0.005% iodine, as a alcoholic solution.

B. 0.01% iodine, as a 10% alcoholic solution.

C. 0.014% sodium chlorite, as a 10% aqueous solution.

D. 0.007% sodium chlorite, as a 10% aqueous solution.

In each instance the indicated amount or preservative added is based on the weight of sugar solid present in the solution.

Each sample was placed in a sterilized jar and permitted to stand, loosely covered, for one month. At the end of this period a very heavy mold had developed on a blank sample similarly prepared and a somewhat lighter mold had developed on Samples A and B. On Samples C and D, to which the sodium chlorite had been added, no mold was observable.

The effectiveness of a chlorite in retarding bacteria, mold and yeast growth has also been demonstrated by its use with heavy melts purposely inoculated with fermenting syrups. To separate samples of the inoculated sugar composition, the preservatives in the proportions indicated in the ioregoing tabulations were added. The chlorite was found in each instance eilective, especially over long periods of time, in preventing or retardlng bacteria, mold and yeast growth, even under adverse conditions indicated, where the composition was purposely inoculated with a termenting syrup to hasten such growth.

The chlorltes may be used with advantage in preserving finished syrups Or the like or in preserving unflnished sugar compositions in transit or awaiting treatment. For such purposes, proportions even as small as 0.005%-0.01%, based on sugar solid content, have been found eflective.

The present application is in part a continuation of my co-pending application Serial No. 380,642, flied February 26, 1941.

Iclaim:

1. In the treatment of sugar compositions, the step comprising subjecting the sugar composition in solution to the action 0! a chlorite in the presence of elemental chlorine.

2. In the treatment of sugar compositions, the step comprising subjecting the sugar composition in solution to the action of a chlorite in the presence of elemental chlorine at a pH of 7.5 to 9.5.

'3. In the refining of sugar melts, the step 0! subjecting the melt at a pH of 7.5 to 9.5 to the action or a chlorite in the presence 01 a nonacidic agent from the class consisting of hypoehlorites and chlorine.

4. In the refining of sugar melts, the step of subjecting the melt at a pH of 7.5 to 9.5 to the action of a chlorite in the presence of a nonacidic agent from the class consisting of hypochlorites and chlorine and thereafter treating the melt with decolorizing carbon.

5. In the refining of sugar melts, the step of subjecting the melt at a pH of 7.5 to 9.5 to the action of a chlorite in the presence of elemental chlorine and thereafter treating the melt with decolorizing carbon.

GEORGE P. VINCENT.

REFERENCES CITED The following references are of record in the flle of this patent:

UNITED STATES PATENTS 

